D1.1 DNA Replication and PCR — Vocabulary Flashcards

Vocabulary flashcards covering key terms from the notes on DNA replication, the semi-conservative model, replication enzymes, origins of replication, PCR, gel electrophoresis, and DNA profiling for forensics and paternity.

DNA replication

The process of producing new DNA strands with base sequences identical to the original; required for reproduction and growth.

Semi-conservative replication

Each new DNA molecule contains one original strand and one new strand; demonstrated by Meselson-Stahl experiments.

Complementary base pairing

A pairs with T and G pairs with C; ensures accurate copying of DNA.

Helicase

Enzyme that unwinds the DNA double helix by breaking hydrogen bonds, often using ATP.

DNA polymerase

Enzyme that catalyses the formation of covalent phosphodiester bonds, adding nucleotides to a growing DNA strand; operates 5'→3'.

DNA polymerase III

Main enzyme in replication that adds nucleotides to the new strand; synthesises DNA.

DNA polymerase I

Enzyme that removes RNA primers and replaces them with DNA.

Primase

Enzyme that synthesises RNA primers to provide starting points for DNA synthesis.

RNA primer

Short RNA sequence (≈10 bases) that provides a 3′-OH for DNA polymerase to begin synthesis.

Okazaki fragments

Short DNA fragments synthesized on the lagging strand, later joined by ligase.

DNA ligase

Enzyme that joins Okazaki fragments by forming covalent phosphodiester bonds.

Nucleotides (deoxynucleoside triphosphates)

DNA building blocks; each carries energy from two terminal phosphates to drive bond formation.

5' to 3' direction

Direction in which DNA polymerase adds nucleotides; strand grows 5'→3' while the template runs 3'→5'.

Leading strand

Strand synthesized continuously in the same direction as the replication fork moves.

Lagging strand

Strand synthesized discontinuously in short fragments away from the replication fork.

Origin of replication

Site where DNA replication begins; multiple origins in eukaryotes speed up replication.

Origin Recognition Complex (ORC)

Protein complex that binds origins to initiate replication.

Meselson-Stahl experiment

Experiment using heavy nitrogen to show semi-conservative replication as the correct model.

Polymerase Chain Reaction (PCR)

Technique to copy a specific DNA segment, amplifying small samples using a thermal cycler.

Denaturation (PCR step)

Heating to separate DNA strands.

Annealing (PCR step)

Primers bind to their complementary target sequences.

Elongation (PCR step)

DNA polymerase copies the target sequence to form new DNA strands.

Taq polymerase

Heat-tolerant DNA polymerase used in PCR.

Thermal cycler

Machine that cycles temperatures to enable PCR amplification.

DNA profiling

Using PCR and gel electrophoresis to identify individuals by DNA fragment patterns; involves restriction digestion.

Gel electrophoresis

Technique that separates DNA fragments by size using an electric field; visualized as bands.

Restriction enzymes

Enzymes that cut DNA at specific sequences to produce fragments of varying lengths.

DNA fragment

Piece of DNA produced by restriction digestion or PCR, varying in size.

DNA fingerprinting

Former term for DNA profiling; now often called DNA profiling or DNA testing.

Forensic DNA profiling

Application of DNA profiling to crime investigations to identify or exclude suspects.

DNA evidence

DNA left at a crime scene used to identify perpetrators or establish relationships.

Paternity testing

DNA profiling used to determine parentage.

Restriction fragment length polymorphism (RFLP)

Pattern of DNA fragments after restriction enzyme digestion used for comparison in profiling.

DNA proofreading

DNA polymerase error-correcting activity that detects mismatches and removes incorrect nucleotides.

Okazaki fragment synthesis

Discontinuous synthesis on the lagging strand; fragments are later joined by ligase.